My invention relates to a clamping device or chuck for axially clamping a tool and, more particularly, to a clamping device for a tool used in a portable powered hand tool, e.g. for a grinding disk in a portable grinding machine.
My invention is based on a chuck for axially clamping a tool, especially a disk-shaped tool or tool disk, on a flange of a driven spindle comprising a clamping nut which is provided with an internal thread and which can be screwed onto an end-side threaded step of the spindle, and a clamping member which is positioned axially between the tool on one side and the clamping nut on the other side and can press the tool against the flange. A clamping fixture of the said type has been disclosed (German Patent Specification No. 3,012,836) in which the clamping member consists of an element which is roughly hat-shaped in cross-section and is axially supported against the flange of the clamping nut via a helical spring. When the clamping nut is screwed on and tightened, the hat-shaped clamping element is pressed axially against the tool via the axially compressed spring, and the tool is thereby tightened against the flange on the spindle side, the end face of a cylindrical extension of the clamping nut coming to bear directly on a facing axial side of the flange on the spindle side and, during further tightening of the clamping nut, the flange on the spindle side being tightened together with the clamping nut. This is to ensure in an angle grinder that the grinding disc is mounted with a definite contact pressure and that this contact pressure remains at the right level. This clamping device is also intended to permit a quick and simple replacement of the grinding disk and at the same time avoid overloading of the powered hand tool, in particular the angle grinder. This is because, if the torque acting on the grinding disk is too great, the grinding disc stops, while the flange and also the clamping nut having the clamping member perform a relative movement thereto. The effect of the clamping nut automatically tightening further in operation, which otherwise makes it considerably more difficult to loosen the clamping nut when changing the grinding disk, is counteracted with this clamping fixture. Nonetheless, loosening of the clamping nut is here only possible with the assistance of a special auxiliary tool. The spindle, depending on the design of the machine, must be appropriately counterheld by a second auxiliary tool, e.g. a spanner.